Yeah, and I've seen it first hand. In South Korea, the US pays South Korea to provide auxiliary troops to support the US military. They are called Katusas. Korean Augmentees To United States Army. The US provides to SKorea the equivalent of E6 pay for each Katusa, even though the individual troops don't receive that. I was earning E3 at the time. I'd have been much happier wasting a year of my life in SKorea had I been receiving E6 pay instead of E3 pay. Plus the AAFES stores and the Commissary were all staffed by locals, giving more money away. I once spent three hours trying to explain the concept of "order a book you don't have in stock" to the cashier at the AAFES Bookstore because the only thing she knew was to say "not on hand" if it wasn't in the store. Then our rations were tightly controlled because so much of what the Commissary and the Class Six were going off base. It wasn't us doing that.
Forget the "they're not paying their fair share of NATO" argument. NATO was never intended for them to pay their fair share. It was always meant to be the US doing the heavy lifting. Financially, manpower, all if it. Trump fundamentally misunderstood NATO when he tried to get the others to pay their promised shares.
Given that, how did the US become the wealthiest country after WWII? Have you forgotten that every other country had its infrastructure blown to smithereens during that war? What was the manufacturing capacity of France, Germany, UK, Japan, or USSR after everything had been bombed? I'm surprised you had to even ask, it is such a well known and obvious result of WWII. It wasn't because they were paying us for protection, it is because we were the only major industrial nation with infrastructure intact. If you wanted manufactured good, it was going to be Made In America. That's why the torch was passed from the UK to the US. It wasn't because other countries were paying protection money.
No, they're not paying for us to defend them. We are paying to defend them. If we're going to throw the lives of our troops away, perhaps we should adopt a more mercenary attitude. The US is broke right now, and all of you think we should still throw our lives and money at everyone else's fight. Quit thinking the US is the indispensable nation. I've long though that if some country wants the US to provide protection, that country should apply for statehood. What I'm suggesting now, a more mercenary attitude, is actually a more moderate position.
Finally, "fight them there or else fight them here" is simple minded sophistry that doesn't even actually support the position of the US as the indispensable world policeman involved in every petty conflict around the globe. The North Elbonians and the South Elbonians are having another slap fight? Gotta send the US to intervene, or the winner will turn around and attack the US? No. Nobody is preparing a major invasion of the US, and nobody is going to be preparing one for a long time. The biggest attack we had in my lifetime was 9/11. We visit that on other countries regularly. Gotta show we're strong by killing brown foreign kids after all.